bpo-47162: Add call trampoline to mitigate bad fpcasts on Emscripten by tiran · Pull Request #32189 · python/cpython · GitHub
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bpo-47162: Add call trampoline to mitigate bad fpcasts on Emscripten #32189

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Merged
miss-islington merged 1 commit into from
Mar 30, 2022
Merged

bpo-47162: Add call trampoline to mitigate bad fpcasts on Emscripten #32189

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27 changes: 27 additions & 0 deletions Include/internal/pycore_object.h
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4 changes: 4 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2022-03-30-13-13-25.bpo-47162.yDJMUm.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,4 @@
WebAssembly cannot deal with bad function pointer casts (different count
or types of arguments). Python can now use call trampolines to mitigate
the problem. Define :c:macro:`PY_CALL_TRAMPOLINE` to enable call
trampolines.
3 changes: 2 additions & 1 deletion Objects/call.c
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Expand Up @@ -211,7 +211,8 @@ _PyObject_MakeTpCall(PyThreadState *tstate, PyObject *callable,
PyObject *result = NULL;
if (_Py_EnterRecursiveCall(tstate, " while calling a Python object") == 0)
{
result = call(callable, argstuple, kwdict);
result = _PyCFunctionWithKeywords_TrampolineCall(
(PyCFunctionWithKeywords)call, callable, argstuple, kwdict);
_Py_LeaveRecursiveCall(tstate);
}

Expand Down
37 changes: 30 additions & 7 deletions Objects/descrobject.c
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Expand Up @@ -13,6 +13,25 @@ class property "propertyobject *" "&PyProperty_Type"
[clinic start generated code]*/
/*[clinic end generated code: output=da39a3ee5e6b4b0d input=556352653fd4c02e]*/

// see pycore_object.h
#if defined(__EMSCRIPTEN__) && defined(PY_CALL_TRAMPOLINE)
#include <emscripten.h>
EM_JS(PyObject*, descr_set_trampoline_call, (setter set, PyObject *obj, PyObject *value, void *closure), {
return wasmTable.get(set)(obj, value, closure);
});

EM_JS(PyObject*, descr_get_trampoline_call, (getter get, PyObject *obj, void *closure), {
return wasmTable.get(get)(obj, closure);
});
#else
#define descr_set_trampoline_call(set, obj, value, closure) \
(set)((obj), (value), (closure))

#define descr_get_trampoline_call(get, obj, closure) \
(get)((obj), (closure))

#endif // __EMSCRIPTEN__ && PY_CALL_TRAMPOLINE

static void
descr_dealloc(PyDescrObject *descr)
{
Expand Down Expand Up @@ -180,7 +199,8 @@ getset_get(PyGetSetDescrObject *descr, PyObject *obj, PyObject *type)
return NULL;
}
if (descr->d_getset->get != NULL)
return descr->d_getset->get(obj, descr->d_getset->closure);
return descr_get_trampoline_call(
descr->d_getset->get, obj, descr->d_getset->closure);
PyErr_Format(PyExc_AttributeError,
"attribute '%V' of '%.100s' objects is not readable",
descr_name((PyDescrObject *)descr), "?",
Expand Down Expand Up @@ -232,8 +252,9 @@ getset_set(PyGetSetDescrObject *descr, PyObject *obj, PyObject *value)
return -1;
}
if (descr->d_getset->set != NULL) {
return descr->d_getset->set(obj, value,
descr->d_getset->closure);
return descr_set_trampoline_call(
descr->d_getset->set, obj, value,
descr->d_getset->closure);
}
PyErr_Format(PyExc_AttributeError,
"attribute '%V' of '%.100s' objects is not writable",
Expand Down Expand Up @@ -306,7 +327,8 @@ method_vectorcall_VARARGS(
Py_DECREF(argstuple);
return NULL;
}
PyObject *result = meth(args[0], argstuple);
PyObject *result = _PyCFunction_TrampolineCall(
meth, args[0], argstuple);
Py_DECREF(argstuple);
_Py_LeaveRecursiveCall(tstate);
return result;
Expand Down Expand Up @@ -339,7 +361,8 @@ method_vectorcall_VARARGS_KEYWORDS(
if (meth == NULL) {
goto exit;
}
result = meth(args[0], argstuple, kwdict);
result = _PyCFunctionWithKeywords_TrampolineCall(
meth, args[0], argstuple, kwdict);
_Py_LeaveRecursiveCall(tstate);
exit:
Py_DECREF(argstuple);
Expand Down Expand Up @@ -427,7 +450,7 @@ method_vectorcall_NOARGS(
if (meth == NULL) {
return NULL;
}
PyObject *result = meth(args[0], NULL);
PyObject *result = _PyCFunction_TrampolineCall(meth, args[0], NULL);
_Py_LeaveRecursiveCall(tstate);
return result;
}
Expand Down Expand Up @@ -455,7 +478,7 @@ method_vectorcall_O(
if (meth == NULL) {
return NULL;
}
PyObject *result = meth(args[0], args[1]);
PyObject *result = _PyCFunction_TrampolineCall(meth, args[0], args[1]);
_Py_LeaveRecursiveCall(tstate);
return result;
}
Expand Down
20 changes: 16 additions & 4 deletions Objects/methodobject.c
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Expand Up @@ -483,7 +483,8 @@ cfunction_vectorcall_NOARGS(
if (meth == NULL) {
return NULL;
}
PyObject *result = meth(PyCFunction_GET_SELF(func), NULL);
PyObject *result = _PyCFunction_TrampolineCall(
meth, PyCFunction_GET_SELF(func), NULL);
_Py_LeaveRecursiveCall(tstate);
return result;
}
Expand All @@ -510,7 +511,8 @@ cfunction_vectorcall_O(
if (meth == NULL) {
return NULL;
}
PyObject *result = meth(PyCFunction_GET_SELF(func), args[0]);
PyObject *result = _PyCFunction_TrampolineCall(
meth, PyCFunction_GET_SELF(func), args[0]);
_Py_LeaveRecursiveCall(tstate);
return result;
}
Expand All @@ -537,7 +539,9 @@ cfunction_call(PyObject *func, PyObject *args, PyObject *kwargs)

PyObject *result;
if (flags & METH_KEYWORDS) {
result = (*(PyCFunctionWithKeywords)(void(*)(void))meth)(self, args, kwargs);
result = _PyCFunctionWithKeywords_TrampolineCall(
(*(PyCFunctionWithKeywords)(void(*)(void))meth),
self, args, kwargs);
}
else {
if (kwargs != NULL && PyDict_GET_SIZE(kwargs) != 0) {
Expand All @@ -546,7 +550,15 @@ cfunction_call(PyObject *func, PyObject *args, PyObject *kwargs)
((PyCFunctionObject*)func)->m_ml->ml_name);
return NULL;
}
result = meth(self, args);
result = _PyCFunction_TrampolineCall(meth, self, args);
}
return _Py_CheckFunctionResult(tstate, func, result, NULL);
}

#if defined(__EMSCRIPTEN__) && defined(PY_CALL_TRAMPOLINE)
#include <emscripten.h>

EM_JS(PyObject*, _PyCFunctionWithKeywords_TrampolineCall, (PyCFunctionWithKeywords func, PyObject *self, PyObject *args, PyObject *kw), {
return wasmTable.get(func)(self, args, kw);
});
#endif
12 changes: 9 additions & 3 deletions Python/import.c
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Expand Up @@ -527,7 +527,7 @@ import_find_extension(PyThreadState *tstate, PyObject *name,
else {
if (def->m_base.m_init == NULL)
return NULL;
mod = def->m_base.m_init();
mod = _PyImport_InitFunc_TrampolineCall(def->m_base.m_init);
if (mod == NULL)
return NULL;
if (PyObject_SetItem(modules, name, mod) == -1) {
Expand Down Expand Up @@ -958,6 +958,13 @@ PyImport_GetImporter(PyObject *path)
return get_path_importer(tstate, path_importer_cache, path_hooks, path);
}

#if defined(__EMSCRIPTEN__) && defined(PY_CALL_TRAMPOLINE)
#include <emscripten.h>
EM_JS(PyObject*, _PyImport_InitFunc_TrampolineCall, (PyModInitFunction func), {
return wasmTable.get(func)();
});
#endif // __EMSCRIPTEN__ && PY_CALL_TRAMPOLINE

static PyObject*
create_builtin(PyThreadState *tstate, PyObject *name, PyObject *spec)
{
Expand All @@ -973,8 +980,7 @@ create_builtin(PyThreadState *tstate, PyObject *name, PyObject *spec)
/* Cannot re-init internal module ("sys" or "builtins") */
return PyImport_AddModuleObject(name);
}

mod = (*p->initfunc)();
mod = _PyImport_InitFunc_TrampolineCall(*p->initfunc);
if (mod == NULL) {
return NULL;
}
Expand Down
6 changes: 3 additions & 3 deletions Python/importdl.c
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Original file line number Diff line number Diff line change
Expand Up @@ -102,7 +102,7 @@ _PyImport_LoadDynamicModuleWithSpec(PyObject *spec, FILE *fp)
const char *oldcontext;
dl_funcptr exportfunc;
PyModuleDef *def;
PyObject *(*p0)(void);
PyModInitFunction p0;

name_unicode = PyObject_GetAttrString(spec, "name");
if (name_unicode == NULL) {
Expand Down Expand Up @@ -157,7 +157,7 @@ _PyImport_LoadDynamicModuleWithSpec(PyObject *spec, FILE *fp)
goto error;
}

p0 = (PyObject *(*)(void))exportfunc;
p0 = (PyModInitFunction)exportfunc;

/* Package context is needed for single-phase init */
oldcontext = _Py_PackageContext;
Expand All @@ -166,7 +166,7 @@ _PyImport_LoadDynamicModuleWithSpec(PyObject *spec, FILE *fp)
_Py_PackageContext = oldcontext;
goto error;
}
m = p0();
m = _PyImport_InitFunc_TrampolineCall(p0);
_Py_PackageContext = oldcontext;

if (m == NULL) {
Expand Down
8 changes: 8 additions & 0 deletions Python/importdl.h
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